Non-starting Mazda 626. Fuel delivery problem?

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Old 10-21-10, 12:09 AM
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Non-starting Mazda 626. Fuel delivery problem?

It's a long story but a lot of it may now be irrelevant. What you do need to know is that this deals with a 1992 Mazda 626 DX Sedan (2.2L, 4 cyl, fuel-injected, manual trans) that's been sitting undriven for about 6 years. When parked it was running fine; no problems.

I've done some repairs, made progress and (I think/hope) I'm now fitting that last piece into place.

The current situation is this:
The fuel pump was broken. I replaced it and then the fuel filter.
The fuel pump is now immersed in fresh gasoline. I've purged (I think, most to all of) the old gas from the lines (pump to filter).

The pump runs and it now gets fuel, at least, as far as fuel filter out (possibly farther but I'm not sure how to check.)

It is getting spark. When starter fluid is sprayed into the air intake it will roar to life for a few seconds.

It seems to be a fuel delivery problem; (my guess) somewhere in area of the fuel rail/injectors. I don't know much about fuel injection systems but my hunch is that it may be related to either air that needs to be bled out of the fuel line or the injectors just not working ..either due to being gummed up from sitting there, unused, with old gas for 6 years or some other reason.

I've read both that you should and should not have to bleed the fuel line after repairs. Also that, when you do bleed the air from the fuel lines, one should use the Schraeder valve to do so. I've also been told that there is no Schraeder valve on a 1992 Mazda 626.

Is there a need to bleed the fuel line? Does this sound like it could be the problem? If so, how do you bleed the fuel line?
How can I test that adequate fuel pressure is being delivered to the fuel rail?

Regarding cleaning the injectors, it seems its usually done preventatively (adding injector cleaner to fuel while the engine is still operating properly or to have them done professionally which, I understand is rather expensive. (For the record, I'm trying to keep costs down as I'm hoping to sell the car, regardless.)
If necessary, is it difficult or is specialized equipment required to remove and clean the injectors

How can I test the injectors?
I could start electrical testing, noid lights, etc. and I probably will, but I don't really suspect electrical problems as much as those that would occur from sitting idle.
Is there a way to physically/visually check to see that fuel is being delivered?


In the event that this makes a difference, in case a "closed system" is required for proper functioning, regarding fuel pressure, air vacuum or similar, I've been testing with parts of the air intake, mass airflow sensor assembly, fuel pump etc. not completely reinstalled and tightened down.


With the key in the ON position, engine not running, I noticed I can hear a slight clickity buzz/humm (like that from a transformer, relay or similar electromagnet) that sounds as though it's coming from directly under the printed "2.2" on the air intake manifold (far left end/ passenger side).

I have no idea whether or not this is normal. It may be coincidental, it may be normal. I don't know but since something in that general area seems to be the problem I thought it worth mentioning.


That the gist of it. I know that there are any number of possible causes for this and that, generally, when trouble-shooting you start with the more common or obvious but, as I said, I'm not too familiar with fuel injection and, frankly, don't know what to try next. I welcome any ideas, input, suggestions, thoughts on how to proceed.

Thanks in advance for any help.
 
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Old 10-21-10, 05:57 AM
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Quote) When starter fluid is sprayed into the air intake it will roar to life for a few seconds.

(Quote) It seems to be a fuel delivery problem; (my guess) somewhere in area of the fuel rail/injectors.


The pump may be new, but the circuit that the pump connects up to is from 1992.

You could have a circuit > wiring > connection issue. Grounds are especially important. [I]

With the key on and engine off do you hear the fuel pump coming on?

Rule out blown fuses, circuit breakers, fusible links, and an operational fuel pump relay.

Confirm a circuit to the fuel pump using a test light.

To do that, back probe the connector at the fuel pump with a test light. Now get a second person to turn the ignition key and crank the engine while you watch the test light. If the test light glows when the engine is cranked then you have a circuit. If it doesn’t glow then there’s an opening somewhere in the circuit.

A fuel pump pressure tester and noid light are helpful tools to have when trying to resolve you particular no start issue. They are mentioned in the links below, which you will find very helpful.


| Repair Guides | Gasoline Fuel Injection System | Electric Fuel Pump | AutoZone.com


| Repair Guides | Gasoline Fuel Injection System | Fuel Injectors | AutoZone.com
 
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Old 10-21-10, 08:28 AM
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The 1992 Mazda fuel pump control is turned on & off by the air vane in the air flow meter. The pump won't run if no air goes thru this meter. These were known for the hose between the filter & the engine to tear & draw air thru the hole & not the air flow meter causing the pump not to run.. Check the hose close..
You can also make the pump run for testing purposes by turning the key on, take the top of the air filter off & push the air vane with your finger..
As ASE states, Check the fuses.. I know there is one under the dash that powers the PCM, but I don't know the position.,, Maybe check them all just for Goofs.. Roger
 
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Old 10-21-10, 10:00 AM
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Either I'm not clear on what you're saying or you didn't read what I wrote.

The pump runs and it now gets fuel, at least, as far as fuel filter out..
I've disconnected the fuel line from the fuel filter outlet, connected a length of tubing, run it into a bottle which, when a second person turned the ignition key and cranked the engine, got filled with gasoline.

The 1992 Mazda fuel pump control is turned on & off by the air vane in the air flow meter. The pump won't run if no air goes thru this meter. These were known for the hose between the filter & the engine to tear & draw air thru the hole & not the air flow meter causing the pump not to run.
On the other hand, if you're saying the air vane in the air flow meter has to be opening, switching an electrical circuit for proper operation, this could be a factor as I know this isn't happening. As I mentioned, the air intake is still partially disassembled. I suppose I could test it with a screwdriver propping it open.

I've done a lot of searching before posting and, though I haven't found many solutions, I have found several other 90's Mazda 626s with very similar problems.

Again, this car was running fine until parked and has since been sitting for over 5 years so I'm leaning more toward the sort of things caused by inactivity: nests, rust, etc.
One guy found a relay full of fried ants, for example.

Any answers to my original questions including bleeding the fuel line and testing for adequate fuel pressure to the fuel rail?

If there are no other suggestions, I'll plan to check fuel pressure and the injectors with noids next.
 
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Old 10-21-10, 12:52 PM
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ActionClaw,

Had I thought this way a vane airflow sensor (or safety switch) issue I would have mentioned it originally.

The vane airflow sensor is located in front of the throttle and monitors the volume of air entering the engine. It does this via a spring-loaded mechanical flap. The flap will push open by an amount that is directly proportional to the volume of air entering the engine. The flap has a wiper type of arm that rotates against a sealed potentiometer. AKA (variable resistor or rheostat) This allows the sensor's resistance and output voltage to change as airflow changes. The greater the airflow, the further the flap will open. This will lower the potentiometer's resistance, and increases the voltage return signal to the ECM. The vane airflow sensor also has a safety switch for the electric fuel pump relay. Airflow into the engine actually activates the fuel pump. If the engine won't start, and the fuel pump is not turning on, the problem may be with the airflow sensor. The check the safety switch, turn the ignition key on and push the flap open. If the fuel pump does not come on, the contact inside the sensor is defective.


Now all that being said, the problem is not the vane airflow sensor.

If it was you wouldn’t have been able to fill your jar with fuel as you stated.

Sounds like the injectors are not firing. [U][I][B]

Sorry, but we can’t take this to the next level, until you answer the questions that continue to go un-answered.
 
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Old 10-21-10, 01:51 PM
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..the problem is not the vane airflow sensor.
I didn't think so either but since
  • I didn't know what other circuits it may be tied into and
  • I don't know what the problem is..
it was easy enough to test and eliminate as a possibility.

Sounds like the injectors are not firing.
Exactly. That's pretty much what I've been saying. As I also stated earlier, I'm no EFI expert and unsure how to proceed troubleshooting; my reason for posting here. I'm trying the NOIDs now.

Sorry, but we can’t take this to the next level, until you answer the questions that continue to go un-answered.
Other than every one of those I have asked, what questions continue to go un-answered?
 
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Old 10-21-10, 02:23 PM
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What questions continue to go un-answered?

Are the injectors firing?
Are there any blown fuses, circuit breakers, or fusible links?
What is fuel pressure PSI reading via a fuel pressure gauge?


 
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Old 10-21-10, 03:04 PM
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The NOIDs say each injector is getting pulse.

To recap, getting spark and will fire when it has fuel, fuel known to be getting as far as the filter outlet, injectors are getting electrical signal.

Whether or not there's sufficient pressure, I don't know. I borrowed a fuel pressure gauge but haven't yet tried it. I've been told there is no Schraeder valve on a '92 626 but haven't yet found whether there's some other pressure test fitting, if so where it is, etc. (Anybody know?)

So back to my original post (unless the fuel pressure tests as too low) the problem "seems to be a fuel delivery problem; (my guess) somewhere in area of the fuel rail/injectors."

How do you bleed the fuel line and/or test fuel pressure is being delivered to the fuel rail?

Can a Fuel Pressure Regulator go bad or get gunked up from just sitting?


(The fuel pumps in the tank but not all sealed up yet) Is a completely "closed system" required to build up adequate fuel pressure?
 
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Old 10-22-10, 05:00 AM
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ActionClaw,

(Quote) fuel known to be getting as far as the filter outlet.

Is there at least half a tank of fuel?

You could have accidentally installed the fuel filter backwards?

You could have accidentally reversed the lines at the fuel pump when you changed it.


Does the fuel line (forward of the filter outlet) look crushed or smashed? Disconnect the line at the outlet and at the fuel rail and blow out the line with compressed shop air.

Correct. There isn’t a schrader valve or test port. You have to make-up (a 3-way “Tee” fitting). to tap into the fuel line. Scroll back [I]and click on the first link [/I](electric fuel pump) I sent you in my first answer. Read it and scroll through it. The first image in the link, shows the fuel pressure gauge connected to the fuel line via a tee.

Pull the rubber vacuum hose on the fuel pressure regulator. If you see fuel inside the rubber hose, it means the diaphragm inside the regulator has ruptured, and the regulator must be changed.
 
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Old 10-25-10, 06:34 PM
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Here's the latest.
I had already established that the pump was functioning, etc. It was pumping fuel; whether or not at sufficient pressure, I didn't yet know. It seemed to me the problem lay somewhere between the fuel filter out and fuel injectors out.

Next, was for me to measure the fuel pressure and try something else I previously didn't know. A service manual for a later year Mazda 626, instructs, after opening the line for pump repairs etc., to run the fuel pump for a full 5 minutes to build up adequate fuel pressure!
To others that others may also find useful. Use whichever method is applicable depending upon the year. For Mazda 626 (and MX-6, Probes & some others)..
  • On ODB2 vehicles, post-1995/96 or so, on Data Link Connector, jumper the F/P terminal to ground, turn the ignition to ON to energize the fuel pump.
  • On ODB0 (ODB1?) vehicles, 1992,93..etc., there's a bundled cable that runs from the firewall forward, between the fuel filter and drivers side strut tower. From it are 2 plastic connectors. One is a yellow plastic, 2 terminal, fuel pump test connector. Bridge the terminals and turn the ignition on to energize the fuel pump.

So, here's what happened:

The 1992 Mazda 626 has no Schraeder valve, or from what I was able to determine, any other type of fuel pressure test port. I connected the pressure gauge to a T-fitting I installed in the fuel line after the fuel filter. It read as no pressure. Hearing the pump running, I waited a few minutes thinking pressure might build. It didn't.

I lifted the access cover a bit, peeked inside and saw fuel being splashed back into the tank.
My first thought was "Could I actually have accidentally reversed the lines when changing the fuel pump?" In addition to the fact that — due to the positioning and differing lengths of the line, that would be very difficult to do — I had already, with this same arrangement, pumped fuel both out of the tank and through the filter.

I shut it off, looked for kinked lines, blockage, etc., disconnected the pressure gauge, replaced it with a clear hose running into a bottle, energized the fuel pump and, once again, fuel flowed through and into the bottle.
I reconnected the pressure gauge, energized the fuel pump but again, had no pressure reading and fuel was again being diverted back into the tank.

I don't know and I could be wrong but, my impression is as though it's meeting resistance at some point and instead of building pressure, coming back out the same hose it's supposed to be pumped out of.

Not a secure seal at the pump outlet? Could another bad component (fuel pressure regulator, for example) cause this sort of behavior?
Ideas? Thoughts? Suggestions?
 
  #11  
Old 10-26-10, 04:43 PM
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An O-ring is used between pump outlet and outlet tube on the assembly. A new O-ring wasn't provided with the new fuel pump and I'm thinking perhaps it may be worn or the size mismatched to the new pump allowing it to spray right back out. I remember it seemed a bit sloppy. I pulled the pump, plan to try to find a replacement at AutoZone or the hardware store, reinstall and try again.
 
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Old 10-27-10, 09:00 PM
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Good News!!

I pulled the fuel pump assembly, dismantled to inspect it. The O-ring looked secure enough but once it's on (or in) you can't really tell how snug a fit there is.
I went to the hardware store to get a new replacement — trying to find a similar but slightly thicker one— but there were none so I picked up several similar but slightly differing sizes. I reinstalled the pump into the assembly using two O-rings thinking that would insure a tighter seal. Put it all back together with the pressure gauge in line (same location, after fuel filter) turned it on and was glad to see a reading (as I recall, it started at around 50 then leveled off at around 34-36). Disconnected the jumper, tried to start it and after just one brief bout of coughing it started right up!! .. and after not having run for years!

One (main!) problem solved but, to get this back on the road, there's still more to do. I may be back.

Thanks for your responses.
 
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